Production of glycerin from sugar by yeast fermentation



Patented Nov. 5, 194 6 PRODUCTION OF GLYCERIN FROM SUGAR BY YEASTFERMENTATIQN Carl Ii. Neuberg, New York, and Irene S. Roberts,Fieldston, N. Y.

No Drawing. Application December 30, 1942,

Serial No.470,636

6 Claims. 1

This invention relates to improvements in the production of glycerinfrom sugar by yeast fermentation.

Two methods are generally known to convert the alcoholic fermentationinto glycerin fermentation. Said methods have been outlined by one ofthe inventors, Carl Neuberg, together with E. Faerber, in 1916. (C.Neuberg and E. Faerber, Bioch. Z. 78,238, Dec. 1916).

According to both of the known methods a glycerin fermentation isobtained by preventing the normally occurring reduction of theacetaldehyde formed intermediary during the fermentation.

The first of said methods is the so-called methd of fixation. It ischaracterized by the application of sulphites. Hereby the intermediarilyformed acetic aldehyde is fixed. The reduction of acetaldehyde isprevented and glycerin is formed according to the following equations:

or, if the action of the sulphite is to be formulated:

(No.2) ourflowuaisoi mo=omcnon somm mncowcmoncnonomon The second method,the method of .dismutation, is based on the addition of any alkalineagents. In this case too, the sugar is decomposed according to EquationNo. I mentioned above into acetaldehyde, carbon dioxide and glycerin.The mutase of the yeast, however, favored by the alkaline reaction,efiects a dismutation of 2 mol. acetaldehyde into 1 mol. acetic acid,and 1 mol ethyl alcohol. The reaction proceeds according to thefollowing equation:

The mechanism of both these methods has been fully described by Neubergand Reinfurth (Bio. Z. 89,365; 92,234, 1918. Neuberg and Hirsch, Bio. Z.96,175; 98,141; 100,804, 1919; see also Beilsteins HandbuchErgaenzungsband I, p. 266, 1928).

The following patents have been issued covering the sulphite method:Cocking and Lilly, U. S. P. 1,425,838, August 15, 1922; Connstein andLuedecke, U. S. P. 1,511,754, October 19, 1924. The bicarbonate methodhas been disclosed by: Eolf, U. S. P. 1,288,398, December 17, 1918.

Since the additions which are substantial for the formation of glycerinare poisonous for the yeast, selected varieties of yeast have to beapplied according to the known processes, e. g.: certain kinds of bakersyeast and .a special wine of the additions on the yeast is reduced. The

yeast. Most of the suggested special kinds of opinion brewers yeast isunsuitable for glycerin fermentation. This certainly holds true forCentral European brewer's yeast.

We have found that ordinary American brewers yeasts which are mostlybottom yeasts, surprisingly, under special conditions, are perfectlysuited for glycerin preparation by fermentation of sugar, when usedtogether with agents adapted to prevent the reduction of acetaldehydeformed intermediary during the fermentation process.

No adaptation of yeast to the medium is necessary if the fermentation isperformed under'the special conditions which are subsequentlydescribed'and which form a part of this invention.

(a) Instead of using brewers yeast only, it is possible to add to thebrewers yeast a small percentage of bakers yeast. per cent. will besumcient.)

(1)) Another necessary condition is to carry out the fermentation undercontinuous mechanical stirring.

(c) Finally, it will be necessary to bubble continuously orintermittently added carbon dioxide through the reaction mass.

By thislatter step a two-fold effect is reached, I namely, a step,namely, a stirring action, and a decrease in pH of the alkaline NazSOstowards the neutral point, whereby any poisonous action use of equalparts of NazSOs and NaHSOa as recommended in Patent No. 1,425,838 isunfavorable. The pH of this mixture is 6.2, which means that there ismuch free H2803 formed by dissociation. This acid is a. very strongpoison for the yeast. The poisonous action is so considerable that thesulphite mixture has to be added in,16 to 18 fractions within from 3 to5 days. The fermentation time' amounts to from 144 to 216 hours.- Thealkalinity of NazSOa, however, can

I be decreased by addition of any acid or acid salts like H2804, HCl,acetic acidor K2S2O5 or. S02

gas phase until a pH of 7.2-7.5 has beenjob- (Generally about 10 3tained. Addition of C02 brings the 7. The solution contains then Duringthe fermentation process the pH will be practically constant. When thereaction product after the fermentation remains at temperatures ofEEO-35 C. a small rise of the pH willoccur on account of a partialtransformation of NaHCOa into NazCOa.

The time required for the complete fermentation under our above namedconditions is considerably shorter in comparison with the formerlyapplied baker's or wine yeast: 24 to 48 hours, as compared to from144-216 hours.

The following examples are given:

pH down to Example 1 100 g. glucose in 500 cc. H20 are mixed with 90 g.brewers yeast (containing 30% dry substance). When fermentation hasstarted 65 g. of waterfree NazSOa in 450 cc. H2O are added in oneoperation under continuous stirring. Temperature: 32-35. minutes afteraddition of sulphite, pH is 7.2. At the end of the fermentationafter 24hours-pH is 7.35. All of the sugar is fermented. Obtained: 13.2 g.acetaldehyde, 26.7 g. glycerin. 22.0 g. ethanol.

Example 2 pH 7.4. Temperature 30-32. Yields: 17.4 g.

As above, instead of the 90 g. brewers yeast,

however, 80 g. are applied, in mixture with 10 g. baker's yeast (drysubstance 34%) Temperature 30-34. Initial pH 7.1; final pH 7.3. Completefermentation after 24 hours. Yields as in Example 1.

Example 3 100 g. glucose in 450 cc. H2O. Start fermentation with 100 g.brewers yeast (dry substance 30%). Add 100 g. NaZSO: in 500 cc. H2O. Addit in two fractions at 2 hours interval. Temperature 33. Continuousaddition of C02, initially in quick stream, slowing down after 18 hours.Sugar completely fermented after 28 hours. pH prior to addition of C027.75, after that 7.2, finally 7.4. Yield: 16.4 g. acetaldehyde, 33 g.glycerin.

Example 4 Same as No. 3, but 88 g. brewers yeast plus 12 g. bakersyeast. Time of complete fermentation: 24 h.; yields practically as inNo. 3.

Example 5 Start fermentation of 100 a. glucose in 500 cc. H2O with 90 g.brewers yeast. Add mixture of 60 g. NazSOa plus 8.6 g. NaHSO: in 450 cc.H20. After 24 h. there is reducing sugar still present as proved withOsts solution. Further addition of 30 g. fresh brewers yeast, undercontinuous stirring. Temperature 33. Fermentation completed after 46hours. Initial pH: 7.05, final pH 7.7. Yields: 13.6 g. acetaldehyde,27.2 g. glycerin.

Example 6 When working on a larger scale, the quantity of yeast appliedaccording to the above examples, can be reduced; If brewers yeast ofgood resistance is applied, the quantities of yeast may be decreased upto A of the quantities quoted heretofore. This holds true if sulphitesare applied. In a purely alkaline solution, as obtained by alkalibicarbonates, the quantity of yeast to be used is to be determined bythe resistance of the particular type of yeast.

Yields of glycerin and acetaldehyde are increased by higherconcentration of the sulphites. However, a higher concentration ofsulphite than mentioned in Examples 3, 4 and 6 is'not rational, sincethe time required for the experiment increases because the addition ofthe agent of fixation can only be performed at considerable intervals.Time for complete fermentation increases also. The sugar not fermentedaccording to Equation No. l undergoes in all cases or-. dinary alcoholicfermentation; accordingly ethanol is formed which is a valuableby-product like acetaldehyde.

The following products are usable as sources of sugar in this process:glucose, saccharose, maltose, invert sugar, molasses, and all suchmaterials or liquids containing the above named sugars. Due to the shorttime (4.5-6 times shorter than in known processes) required for thecomplete. fermentation according to this process only few impuritiesfrom dead and autolyzed yeast cells will enter the solution. Theisolation of glycerin can therefore be performed in a simple way.

If brewers yeast has been applied, the fermentation mixture is clear toa substantial degree by spontaneous sedimentation of the yeast. Theliquid on top can easily be clarified by filtration or centrifugation.(If yeast sediments poor- 1y, quick results can be obtained by addingapproximately 5% of'the weight of the originally applied sulphite ofCaClz or Bach, or FeSOr, Fez(SO4)3, A12(SO4)3 or fuilers earth, etc., tothe glycerin beer.) The rest of the solution containing glycerin istreated in the same way, i. e.: centrifugation or filtration from theyeast mash. The acetalydehyde and ethyl alcohol formed simultaneouslywith the glycerin are isolated by distillation according to the knownprocesses. The glycerin solution is further concentrated and eithertreated in an atomizer until a thick product is obtained which isinterspersed with the various salts previously added or formed duringthe process respectively (NaHCOa from NazSOa), or concentrated further,preferably in vacuo. From said residues a rather pure glycerin can beobtained by extraction. Suitable solvents for extractions are forinstance: ethyl alcohol (for example the ethanol containingacetaldehyde,

as obtained simultaneously in the process of fermentation itself), orbutanol, isopropyl alcohol, isobutyl alcohol, benzyl alcohol,cyclohexanol, its homologues, furfuryl alcohol, terahydrofurfurylalcohol.

In presence of small quantities of ethanol the following solvents aresuitable: dioxane, methylpropylketone, methyl-isopropyl-ketone,methylhexyl-ketone, ethyl acetate, amyl acetate. Hot or' cold extractionmay be performed, preferably under mechanical stirring. The solvents arerecovered by simple fractionation, in vacuo if necessary. The glycerinwhich has been freed of the salts by the above mentioned solvents isthen refined. If working withsolvents which will not mix readily withwater, the glycerin, by shaking with water, can be transferred into thewater fraction. Impurities will stay in the solvent. In either case, adifficult purification of themash by means of acids, alkalies, earthalkalies, metal salts, as previously used, is unnecessary. This processavoids heating to high temperatures with superheated water vapor, anddecomposition of glycerin and formation of bad smelling products formedby the decomposition of glycerin and its accompanying impurities.

We have described preferred embodiments of this invention, but it willbe understood that various changes will be made without departing fromthe scope of this invention.

What we claim is:

1. In the process of producing glycerine by fermentation of sugar withyeast, in which the reduction of acetaldehyde formed intermediary duringthe fermentation process is prevented by known means, the combination ofthe steps comprising generally the use of commercial brewers yeast in anamount exceeding the amount of yeast merely sufiicient for thefermentation of the given amount of sugar; continuously stirring thereaction mass; bubbling added carbon dioxide therein; and maintaining apH of 7.2-7.5 during the reaction.

2. In the process of producing glycerine according to claim 1, the useof a mixture of about per cent. of commercial brewers yeast and about 10per cent. of bakers yeast.

3. A method of producing glycerine by yeast fermentation according toclaim 1, comprising the use of sulphite in the fermentation process towhich acid salts are added until a pH of 5.2-7.5 has been obtained.

4. In' the process of producing glycerine by yeast fermentation of sugarwhich comprises continuously stirring the reaction mass and hubblingcarbon dioxide through the reaction mass, which contains commercialbrewers yeast and sulphites, the concentration of the glycerine formedby evaporation'and the eirtraction of the same with solvents of theclass consisting of aliphatic-mono-alcohols, aromatic-mono-alcohols, andhydro aromatic-monoalcohols which are insoluble, or barely soluble, inwater.

5. A process according to claim 4 comprising the extraction of theconcentrated glycerine with cyclohexanol.

6. A process according to claim 4 which comv prises extraction of theconcentrated glycerine with benzyl-alcohol.

CARL A. NEUBERG. IRENE s. ROBERTS.

